Generally, a conventional heating, ventilating, and air conditioning (HVAC) system utilizes predetermined and/or fixed set-points for control of heat pump and fluid pump operations, while relying on local fan-coil unit controllers for localized control. For example, FIG. 1 illustrates a conventional HVAC system. As illustrated, the system 100 includes a heat pump 101, fluid pump 102, three-way valve 103, and a plurality of fan-coil units (FCUs) 120. Each fan coil unit may include a proportional valve 104 and variable speed fan-coil heat exchanger 105. In the HVAC system 100, a heat transfer fluid may flow through each component to provide cooling or heating according to well-known manners. The heat transfer fluid may be any suitable heat transfer fluid or refrigerant, including water.
The heat pump 101 provides heating or cooling according to a predetermined or user-defined fixed-value of leaving water temperature (LWT). The heat pump adjusts cooling capacity based on entering water temperature (EWT) and LWT in order to maintain the associated LWT. The water pump 102 controls water flow based on pressure drop across the fan-coil units 120. The three-way valve 103 by-passes surplus water flow to maintain minimum water flow required by heat pump 101. In system 100, the valve position and the fan speed of each FCU may be used for controlling a different conditioned space's temperature.
In conventional implementations, the fixed LWT and pressure set-points of HVAC systems result in short-comings which include capacity which may not fully and quickly match an actual load. Thus, HVAC systems are not operated in the most energy efficient condition. Further, in HVAC systems where set-points are assumed to be varied based on steady-state load conditions, power consumption changes associated with equipment wear and equipment variances are not adequately considered. Moreover, even if a LWT set-point is routinely reset based on ambient temperature, internal load changes are not considered on the fly.